Quick answer
Commercial HVAC loses efficiency over time through dirty filters and coils, slipping belts, drifting sensors, valves that pass water, heating and cooling fighting each other, and time schedules that no longer match occupancy. Most of these are fixed through routine maintenance and a controls review, often without capital spend. Measure first, then prioritise the largest and cheapest fixes.
Where efficiency is lost
| Cause | Effect | Typical fix |
|---|---|---|
| Blocked filters | Fans work harder, airflow falls | Filter changes on pressure drop |
| Dirty coils and condensers | Poor heat transfer, higher compressor energy | Coil cleaning, especially pre-summer |
| Slipping or worn belts | Lost fan output, wear | Tension, alignment, replacement |
| Drifting sensors | Plant chases the wrong temperature | Calibration checks |
| Passing valves | Unwanted heating or cooling | Valve and actuator repair |
| Simultaneous heating and cooling | Plant fights itself | Deadbands and setpoint review |
| Schedules out of date | Plant runs when empty | Match schedules to occupancy |
| Overrides left on | Plant stuck in manual or “on” | Override audit |
| Refrigerant undercharge | Lower capacity, longer run times | Leak repair by F-gas engineers |
Controls: the biggest lever
In many buildings the largest savings come from controls rather than equipment. Common issues include:
- plant scheduled for 24/7 operation when the building is used 8am to 6pm
- hybrid working patterns not reflected in floor-by-floor schedules
- manual overrides that were never removed
- no optimum start, so plant starts far earlier than needed
- fresh-air rates fixed at maximum regardless of occupancy
A review of HVAC controls often pays back quickly.
Use the data you already have
If you have a BMS, trend logs show run hours, temperatures and valve positions. Look for plant running at night, valves open in both heating and cooling, and zones that never reach setpoint. Pair this with meter data where available.
Maintenance that protects efficiency
- filters changed on condition, not just by date
- condensers and coils cleaned before peak seasons
- belts and bearings checked
- sensors calibrated annually
- refrigerant leaks found and fixed promptly
Compliance links
Larger air conditioning systems need TM44 inspections, which include advice on improving efficiency. Landlords of non-domestic property must meet the Minimum Energy Efficiency Standard, and HVAC performance affects EPC ratings.
Next steps
An HVAC system assessment identifies where your plant is losing efficiency. Planned maintenance keeps the gains.
Frequently asked questions
How much energy can better HVAC maintenance save?
It depends entirely on the starting point. A neglected building with plant running around the clock may see large savings from schedules alone; a well-run building may see little. Measure and trend energy use before and after changes.
Are EC fan upgrades worth it?
EC fans are generally more efficient and controllable than older AC motors with belt drives, especially at part load. The payback depends on running hours and the existing equipment, so assess unit by unit.
UK guidance and references
Primary and industry sources relevant to this subject. Always check the current edition and how it applies to your building.
This guide is general information for commercial building operators. It does not replace an assessment of your building by a competent engineer. If there is an immediate risk to people, contact the emergency services first.